Interpretive Summary: There is considerable variation in cultivated peanut and there are four market types, Spanish, Runner, Peruvian and Valencia. Most cultivated peanuts in the world belong to Spanish and Runner types, and these two types of peanut exhibit genetically determined variation for a number of botanical and agronomical traits including branches and flowers habits, seed dormancy, and maturation time. The objective of this study was to apply protein profiles to assess diversity of seed proteins in peanut. Total proteins extracted from seeds of 12 different genotypes of cultivated peanut, comprised of Runner market type and Spanish-bunch market type, were separated by electrophoresis on both one-dimensional and two-dimensional SDS-PAGE gels. The protein profiles were similar on one-dimensional gels for all tested peanut genotypes. However, peanut genotype A13 missed one 35 kDa major allergen protein. There was one 27 kDa minor protein that presented in all Runner-type peanuts and the derivatives that have a Runner-type peanut in their pedigree. Among more than 150 main protein spots on the 2-D gels, four protein spots showed polymorphic patterns between Runner-type and Spanish-bunch peanuts. These four protein spots were sequenced. Based on the sequences, these proteins are isoforms of each other, which are iso-allergens. The results revealed that these proteins exhibit polymorphism between subspecies of cultivated peanut, and these proteins could be used as markers.

Technical Abstract:
Total proteins extracted from seeds of 12 different genotypes of cultivated peanut (Arachis hypogaea L.), comprised of Runner market type and Spanish-bunch market type, were separated by electrophoresis on both one-dimensional and two-dimensional SDS-PAGE gels. The protein profiles were similar on one-dimensional gels for all tested peanut genotypes. However, peanut genotype A13 missed one major band with a molecular weight of about 35 kDa. There was one minor band with a molecular weight of 27 kDa protein that presented in all Runner-type peanut genotypes and the derivatives (GT-YY7, GT-YY20, and GT-YY79), which have a Runner-type peanut in their pedigree. The 35 kDa protein in A13 and the 26 kDa protein in Runner-type peanut genotypes were confirmed on the two-dimensional SDA-PAGE gels. Among more than 150 main protein spots on the 2-D gels, four protein spots that were individually marked as spot 1- 4 showed polymorphic patterns between Runner-type and Spanish-bunch peanuts. Spot 1 (ca. 22.5 kDa, pI 3.9) and spot 2 (ca. 23.5 kDa, pI 5.7) were observed in all Spanish-bunch genotypes, which were not found in those of Runner types. In contrast, spot 3 (ca. 23 kDa, pI 6.6) and spot 4 (ca. 22 kDa, pI 6.8) presented in all Runner type peanut genotypes but not in Spanish-bunch type genotypes. These four protein spots were sequenced. Based on the internal amino acid sequences and N-terminal sequences, these proteins are isoforms of each other, which are iso-allergens and may be modified by post-translational cleavage. The results revealed that these storage protein isoforms exhibit polymorphism of the subunit composition between subspecies of cultivated peanut, and these proteins could be used as markers for identification of Runner and Spanish-bunch type peanuts.